Technology update

Nanorod devices fit solar spectrum

A recent report in Science describes how plastic
solar cells could make solar energy more
affordable.

Plastic solar cells based on inorganic nanorods and
semiconducting polymers could make solar energy
more affordable, according to scientists in the US
(Science295 2425).

The devices, developed by Wendy
Huynh and colleagues at the
Lawrence Berkeley National
Laboratory, combine the
affordability of plastic-based cells
with the efficiency of
semiconducting nanorod-shaped
molecules. By adjusting the thickness of the rods, the
energy range for absorbing incoming photons can be
tuned.

The team's hybrid solar cells had a power conversion
efficiency of 6.9%. Using CdSe nanorods measuring
7 nm by 60 nm to optimize the overlap of solar
emission and cell absorption curve resulted in a 6.9%
monochromatic conversion efficiency at 515 nm.

To improve on the devices, Huynh's team plans to
reduce charge recombination by enhancing carrier
mobilities. This could be achieved by improving the
nanocrystal-polymer interface to remove nanorod
traps, making the nanorods longer, and aligning them
perpendicular to the substrate.